Electrostatic voltage multiplier



INVENTORS ATTORNEY CARL BOSCH MORRIS H. SHAMOS 30 23 lfG I r 1 ETAL- c.BOSCH ELECTROSTATIC VOLTAGE MULTIPLIER Flled Sept 1 1950 FIG 3 Sept. 16,1952 Patented Sept. 16, 1952 UNITED sTAT s PATENT OFFICE ELECTROSTATICVOLTAGE MULTIPLIER Carl Bosch, Westfield, N. J., and Morris H. Shamos,New York, N. Y., assignors to Chatham Electronics Corporation, Newark,N. J., a corv poration of New Jersey Application September 1, 1950,Serial No. 182,876

Claims. (01. 171-329) This invention relates to electrostatic voltagemultipliers, and has particular reference to machines which employrotors to carry electrical charges from one capacitor to another. Thedevices hereinafter described are especially suited for use with voltagesources of very high impedance; that is, voltage supply circuits whichare incapable of furnishing enough power to operate a meter.

It is a well known fact that if an electrical charge be moved from aregion oi high capacity to one of low capacity, the voltage will beincreased in proportion to the inverse ratio of the capacities. Thisfact is the basis of design of most of the static influence generators.

Influence generators employing rotating glass disks used a feed backcircuit to effect a continuous build-up in voltage until a breakdownoccurred; The present voltage multipliers are carefully shielded fromall feed back and produce a predetermined voltage ratio which does notexceed an establishedvalue.

One of the characteristics of static influence generators and other,machines employing rotary members is the long period of time necessaryto establish equilibrium. A single stage rotary voltage multiplier ofhigh gain may take over twenty seconds to reach its final value, a'timeinterval which is too'long ior most classes of measurement. One oftheobjects'oi this invention is to provide an improved voltagemultiplier which lowers the time interval necessary to reach a stablevalue.

Another object of the invention is to provide a voltage multiplier whichextracts a negligible amount of current from the input supply circuit.

.Another object of the invention is to provide a small portable voltagemultiplier, convenient to handle, for measuring the potentials ofelectrically charged bodies. v

The invention comprises a plurality of rotatable insulated disks mountedon a single shaft and turned by a motor. Each disk carries a number ofconducting sectors arranged around the disk periphery. Two statorinduction plates are mounted adjacent each disk, one plate whichreceives the input charge and a second which collects the charge andtransfers it to another disk or to an external load circuit. I

For a better understandingoi the present invention, together with otherand further objects thereof, reference is made to the followingdescription taken in connection with the accompanying; drawings.

Fig. 1 is a side view of one of the rotors, showing the input and outputcircuits, and the two induction plates.

Fig. 2 is a cross sectional view of the rotor of Fig. 1, taken alongline 2-2'of that figure.

Fig. 3 is a side view of a three disk voltage multiplier, showing theinput and output circuits. and the wiring of the interstage connections.

Referring now to Figs. 1 and 2, a rotor disk I0. made of insulatingmaterial, is secured to a shaft II. A plurality of conducting sectors I2are fastened to the disk periphery and extend on both sides of the diskas well as across the edge. An input brush I3 is mounted on thestationary frame so as to make electrical contact with the edge portionsof the sectors I2 as the disk revolves and an input induction plate 14is mounted on the frame to act as a capacitorwith the sectors whichrotate through its field.

On the opposite side of disk I2 a second stator plate I5 is secured,together with a second brush I6. The capacitance between the rotor plateand the input plate in the output position is considerably less thanthat in the input or charge position since their inverse ratiosdetermine the voltage multiplying factor. In some cases the plate I5 hasbeen eliminated, using only the brush as the output capacitor.

In order to describe the operation of this device, let it be assumedthat the disk is rotated at a fixed speed and that a voltage of 10 voltsis applied at the input terminals I'I. Then the sectors I2 passingadjacent to sector plate I4 are charged up by influence due to theconnection made through brush I3. When contact with the brush is broken,a charge corresponding to a voltage of 10 volts is isolated on eachsector and is carried by the sectors tothe second plate I5 and brush I6.As the sectors leave the vicinity of plate I4, their potential is raiseddue to the decrease in capacitance, and as the sectors approach plateI5, their potential is still further increased until the predeterminedmaximum is reached at a position adjacent to plate I5. Output terminalsI8 are connected to ground and to brush It. A load circuit, such as anelectrostatic voltmeter, may be connected to these terminals.

When the machine is first started, the second plate I5 is uncharged anda number of sectors must be rotated through the field of capacitor plateI5and in contact with brush I6 before the brush and plate assume theirfinal value. The time required for the voltage build-upv depends uponthe speed of rotation, the ratio of the stator plate capacitances andthe load capacitance.

3 The current flowing through the multiplier due to the chargestransferred by the rotor segments is I faVACA where I is the currentamperes;

a is the number of segments on the disk;

1 is the frequency in revolutions per second; VA is the input voltage;and

CA is the input capacitance.

Ce is the capacitance in the output position relaf tive to the inputplate. 7 r

The equivalent resistance 'R of the device-is 'r iafc ag vcgacapacitance oi output'elecitrode to gr un It hasbeen feun that thetime constants t r sing e disk machi away; be u e l g. specially ostaticvoltmeter and tiukeep the A a three diskdevic as construc ed s l'atedinF-ie- .3. A cen ral sh ft s, retatab y rnounte in side plates 20,2|, and cartie sthree'disks Hid, I019, and e eh e1cie et s?-Z,? s the tr M disk i hre e me tm a l i ei eue ins sree e d. E e v r arries aumber; o cen u t n s eter; pla s Z 12b, and He y h te el ri ener a a ier d item an. input i cuit to an output circuit. An 1 .9 i 1 e 4e sseasonal ty as em l 24 which in turn is supportedby atop conductingPlate 1 W ich else ete eee. i le pla An inp t bru h lricv isjmeunted sos to make emtaet with eachseeter as it pa sesintejthe ield i th t tor Pa n t e QPZ 1$ thedisk an output st.ator plate a s s c r an in u at r Wte s il eieme l on a bas p at 21- Theeutput br sh l eis ount nthe sameelative pos tion withpect teth Output p at es he ru h, i l e- 1m l Theoutput conductor from the first sta e is applied to theinputstatorplate, 4b of the second sta e, and the input brush I31? is grounded Aninsulator support28. carries the input plate. The output section or thistage is similarto the output section of the first. stage; the statorplate 1 b ing mounted on insulat r 0. and connected to brush lBb.Theou'l ljlt circuit of the second stage i d rectly conne ted to the putcircuit of t ast s age. and th, third output circuit is connected to twoterm nals 33 which serve to apply the amplified voltage to a loadcircuit.

In order to make the three stagevoltage multiplier fast acting (have ashort-timeconstant) the design includes several features which causea'rapid voltage build-up. *The gain per stage G is made low sincetheti'me constant varies directly as this quantity. Also, theoutput-capacitance Cg is made as low as possible, since this, too;

4 lowers the time constant in direct ratio. The input capacitance couldbe increased to cause a further time constant reduction of the unititself, but this would also increase the time constant of the inputcircuit. An optimum is attained if both time constants are equal.

I The approximate relationship of the overall time constant Ta to the"time" constants of the separate stages T1, T2, and T3 are given by theformula,

T =VE R+T2 +T if If all the separatestages have the same timeconstant-the ealization reduces to Amore detailed liscussion of theabove problem may be found in Electronics Experimental Techniques byElmore, and Sands, McGraw-Hill Book C0,, New York, 1949, page 139.

If G1 is thegain of a single stage and all the stages: have an equalgain then the'overalligain To make the-overall .gainoi tea number oistages the same as that of asinglestaaeq,

Then the overall time constant H 7 Thus roe-e1 1 values or Y which areless, than 'i'ithiereis. an, improvement in the time constant. If thereare three stages with an overallga'inbi thejtlme constant isone-'twelith of the'time constant of asingle stage having the samegain;*jNumerousexperiments conducted with singe and triplesta'gemultipliers have verified the above relationship.

It is possiblejto"c'ausethe last'orFoutput stage to provide .currentf'toan'external load'by applying a high input, 'voltageito this stage. so asto make the, "quantity on charge transported per revolution reasonablyhigh; In this method of operation the current "supplied depends upon theinput voltage, the capacitance of the input plate. andthe speed or'therotonj Assuch, the stage provides no voltage gain but serves only totransport charges from the 'last'amplifier' stage having a highimpedance to the load having a relatively low impedance. Y,

While the voltage, multiplier described above is particularly adaptedto, be used with; instruments for detecting an'cl'"in'ea'sliringpenetrating radiation, it"is obvious that i-it could -be'usedin anyapplication which calls fora direct-current am-- plifier. As described,the multiplier gain independent of the rotary speed foi the disks Withinwide limits. g

While the above-description'has been limited to a'single and threestagemultiplier; it will be obvious that any number of "stages'may bebuilt without departing from-the field, or the invention which should belimited 'only' by the scope of the appended claims We claim:

l.; An electrostatic 1 voltage} multiplier for producing outputpotentials having -a predetermined ratio to inputpotentials-"comprising; a rotatable insulator, a plurality of conductingsectors secured to said insulator, an input circuit including a statorconducting plate'mou'nted adjacent to the conducting sectors and acontact brush which makes successive contact with the rotatable sectors,and an output circuit including a stator conducting. plate mountedadjacent to the conducting sectors and connected to a contact brushwhich makes successive contact with the rotatable sectors as they moveinto the potential field of the output stator plate.

2. An electrostatic voltage multiplier for producing output.potentialshaving a predetermined ratio to input potentials comprising,a frame. for journalling a rotatable shaft, a disk shaped insulatorsecuredto the shaft, a plurality of conducting sectors secured to saidinsulator, an input circuit including a stator conducting plate mountedon the frame adjacent to the conducting sectors and a contact brushwhich makes successive contact with the rotatable sectors, and an outputcircuit including a stator conducting plate mounted on the frameadjacent to the conducting sectors and connected to a contact brushwhich makes successive contact with the rotatable sectors as they moveinto the potential field of the output stator plate.

3. An electrostatic voltage multiplier for producing output potentialshaving a predetermined ratio to input potentials comprising, a frame forjournalling a rotatable shaft, 9, disk shaped insulator secured to theshaft, and a plurality of conducting sectors secured to said insulatorfor carrying charges from an input circuit to an output circuit, saidinput circuit including a stator conducting plate mounted on the frameadjacent to the conducting sectors and a contact brush which makessuccessive contact with the rotatable sectors, said output circuitincluding a stator conducting plate mounted on the frame adjacent to theconducting sectors and connected to a contact brush which makessuccessive contact with the rotatable sectors as they move into thepotential field of the output stator plate.

4. An electrostatic voltag multiplier for producing output potentialshaving a predetermined ratio to input potentials comprising, a frame forjournalling a rotatable shaft, a disk shaped insulator secured to theshaft, and a plurality of conducting sectors secured to said insulatorfor carrying charges from an input circuit to an output circuit, saidinput circuit including input terminals for receiving potentials from anexternal source and a stator conducting plate mounted on the frameadjacent to the conducting sectors, a contact brush connected to theinput circuit for making successive contact with each rotatable sector,said output circuit including a stator conducting plate mounted on theframe adjacent to the conducting sectors and connected to a contactbrush which makes successive contact with each rotatable sector as itmoves into the potential field of the output stator plate.

5. An electrostatic voltage multiplier for producing output potentialshaving a predetermined ratio to input potentials comprising, a frame forjournalling a rotatable shaft, a disk shaped insulator secured to theshaft, and a plurality of conducting sectors secured to said insulatorfor carrying charges from an input circuit to an output circuit, saidinput circuit including input terminals for receiving potentials from anexternal source and a stator conducting plate mounted on the frameadjacent to the conducting sectors, a contact brush connected to theinput circuit for making successive contact with each rotatable sectoras it is moved into the potential field of the 6 stator input plate,said output'circuit including a stator conducting plate mounted on theframe adjacent to the conducting sectors and connected to a contactbrush which makes successive contact with each rotatable sector as itmoves into the potential field of the output stator plate.

6. An electrostatic voltage multiplier for producing output potentialshaving a predetermined ratio to input potentials comprising, a frame forjournalling a rotatable shaft, a disk shaped insulator secured totheshaft, and a plurality of conducting sectors secured to saidinsulatorfor carrying charges from an input circuit to an output circuit, saidinput circuit including input terminals for receiving potentials from anexternal source and a stator conducting plate mounted on the frameadjacent to the conducting sectors, a contact brush connected to theinput circuit for making successive contact with each rotatable sectoras it is moved into the potential field of the stator input plate, saidoutput circuit for delivering multiplied potentials to an externalcircuit, said output circuit including a stator conducting plate mountedon the frame adjacent to the conducting sectors and connected to acontact brush which makes successive contact with each rotatable sectoras it is moved into the potential field of'the output stator plate.

7. An electrostatic voltage multiplier for producing output potentialshaving a predetermined ratio to input potentials comprising, a pluralityof rotatable insulator assemblies, a plurality of conducting sectors oneach insulator, an input circuit for each rotatable insulator assemblyincluding a stator conducting plate mounted adjacent to the conductingsectors and a contact brush which makes successive contact with therotatable sectors, an output circuit for each rotatable insulatorassembly including a stator conducting plate mounted adjacent to theconducting sectors and connected to a contact brush which makessuccessive contact with the rotatable sectors, and connecting meansbetween each rotatable assembly for delivering the output of oneassembly to the input circuit of another assembly.

8. An electrostatic voltage multiplier for producing output potentialshaving a predetermined ratio to input potentials comprising, a frame forjournalling a rotatable shaft, 2. disk shaped insulator secured to theshaft, a plurality of conducting sectors secured to the periphery of thedisk and insulated from each other, an input circuit for receivingvoltage values from an external source, said input circuit comprising astator conducting plate mounted on a frame adjacent to the conductingsectors, a contact brush connected to the input circuit for makingsuccessive contact with each sector, means for adjusting the inputcapacitance so as to control the voltage gain, an output circuit fordelivering electrical power to a load circuit comprising a statorconducting plate mounted on the frame adjacent to the conductingsectors, and a contact brush for making successive contact with eachsector as it moves into the potential field of the output stator plate.

9. An electrostatic voltage multiplier having a plurality of multiplierstages for producing output potentials having a predetermined ratio toinput potentials comprising; a frame for journalling a rotatable shaft;a plurality of insulating disks, one for each stage, secured to theshaft; a plurality of conducting sectors secured to each disk andinsulated from each other; an input cir- Cult for each 'of said stageswhich includes a stator conducting plate mounted adjacent to theconducting sectors and an input contact brush which makes successivecontact with the rotatable sectors; an output circuit for each of saidstages which includes a stator conducting plate mounted adjacent tothe'conducting sectors and an output contact brush connected to thestator plate for making successive contact with the rotatable sectors;input terminals connected to the input circuit of one of the stages'forreceiving poten= tials from an external circuit; output terminalsconnected to the output circuit of one of the stages for applying apotential to an external load circuit; and intermediate -couplingcircuits for'connecting. the output circuit of one stage to the inputcircuit of another stage.

10. An electrostatic voltage multiplier having a plurality of multiplierstages for producing out put potentials having. a predetermined ratio toinput potentials comprising; a frame for journal ling a rotatable shaft;a plurality of insulating disks, one for each stage, secured to theshaft; a plurality of conducting sectors secured to each disk andinsulated from each other; an in ut circuit for each of said stageswhich includes a stator conducting plate mounted adjacent to theconducting sectors and an input contact brush which makes successivecontact with the rotatable sectors; an output circuit for each of saidstages which includes a stator conducting plate mounted adjacent to theconducting: sectors and an output contact brush connected to the-statorplate for making successive contact with the rotatable sectors; inputterminals connected to the input circuit of one of the stages forreceiving potentials from an external circuit; output terminalsconnected to the output circuit of one of the stages for" applyingapipotehtial to an external Ioadrcireuit; and intermediate couplingcircuits for connecting the output circuit of orie'sta'ge to the inputcircuit or another stage; saidout= put stage having a voltagemultiplying. factor of aboutunity as'a result crproviding output ci1r=rent ror" use ina current consuming load circuit. a a ia osena MORRISI-l; SHAMQS; Y J REFERENCES CITED The foliowizig r ferences-streetrecord the file of thiszp'atent'z.

' UNITED STATES l' A l -ENT S I Number Name Date tracer enry l Aug; 2,11 892 295235 9 Felic a :Sept. 26,11'950

